The application of new metrics for understanding trends in undiagnosed HIV among key populations

Objective: Investigate the utility of novel metrics for understanding trends in undiagnosed HIV.

Methods: We produced estimates for the number of people with undiagnosed HIV and the number of new HIV infections using Australian surveillance data and the European Centre for Disease Prevention and Control HIV modelling tool. Using these estimates, we calculated: the total diagnosed fraction, the proportion of all people with HIV diagnosed; the yearly diagnosed fraction, the proportion of people who have not yet received a diagnosis who received a diagnosis during each year; and the case detection rate, which is the annual ratio of new HIV diagnoses to new HIV infections each year; from 2008 to 2019. We report trends in these metrics for Australian-born and overseas-born men who reported male-to-male sex and heterosexual women and men.

Results: Each metric for the Australian-born male-to-male sexual contact group improved consistently. In contrast, the metrics for the overseas-born group worsened (total diagnosed fraction: 85.0-81.9%, yearly diagnosed fraction: 23.1-17.8%, and case detection rate: 0.74-0.63). In heterosexuals, women and men had consistent increasing trends for the total diagnosed fraction and yearly diagnosed fraction but with women having consistently higher estimates. Heterosexual men had a declining case detection rate, falling to less than one in 2011, compared to an increase for women.

Conclusions: The additional metrics provided important information on Australia's progress toward HIV elimination. The more dynamic changes in the undiagnosed population seen highlight diverging trends for key populations not seen in the total diagnosed fraction.